1. Field of the Invention
The present invention relates to a roller bearing cage applied to, for example a lower, larger end called a rod xe2x80x9cbig endxe2x80x9d of a connecting rod in an engine and more particularly to a roller bearing cage suitable for use in a split shell roller bearing designed to fit around a crankshaft in which crankpins are made integrally with crank webs.
2. Description of the Prior Art
As the modern engines are needed to get further higher in horsepower, the crankshaft for the powerful engines has to be made so as to stand up to further high-speed revolution. To cope with this, the crankpins are made integral with the crank webs to enhance the rigidity or stiffness of the crankshaft. Split shell roller bearings, because of the integral construction of the crankpin with the associated crank webs, are inevitably required at the rod big-ends of the connecting rods and correspondingly the cage is also needed to be made in any split type. High-compression, high-speed engines, moreover, impose very harsh conditions to the bearings.
An example of conventional bearing cages is disclosed in Japanese Patent Laid-Open No. 219149/1996. The prior bearing cage is made in a configuration resembling any gate in cross section and envisaged to carry effectively the loads imposed by modern high-speed engines. To this end, the cage is made on the outside periphery thereof with the retaining projections to keep the rollers against their escape out of the cage.
Another example of the bearing cage having a gate-like configuration in cross section is disclosed in Japanese Utility Model Laid-Open No. 168014/1989. The prior bearing cage is also directed to keep the rollers against their escape out of the cage, thereby carrying well the heavy loads imposed by high-speed engines. To this end, the bearing cage, as illustrated in FIG. 1 of the above citation, has a partition separating two adjacent pockets, the thin area of which is made with projections that extend inside the pockets slightly beyond the flanks of the thickened areas to serve for keeping the rollers against their radially outward escape out of the cage.
Japanese Patent Laid-Open No. 240660/2000 discloses a roller bearing retainer split into two haves, which is favorable for the crankshaft having crankpins formed integrally with the crank webs. The prior roller bearing retainer is designed in such a way reduced in an outside diameter thereof as nearing the diametral opposing abutment ends of the retainer halves to be made in a somewhat oval shape. The construction recited above is envisaged to keep the retainer against any unfavorable deformation where the retainer may get bulged radially at the diametral opposing abutment ends of the retainer halves.
Another split type of the roller bearing cage is disclosed in Japanese Utility Model Laid-Open No. 6746/1994, in which an annular cage of true round is split into two halves along a diametral plane lying on the circumferential midway points of any two diametral opposing cage bars. The cage halves are covered with any coating material of a preselected thickness at their at least any one side of split ends that come into circumferential abutment against one another.
Moreover, Japanese Patent Laid-Open No. 72332/1997 discloses a connecting-rod bearing construction for marine engines, in which a needle bearing for a rod big-end is composed of a pair of semicircular cage halves, which come into abutment against each other to form a completely circular cage.
None of the prior bearing cages of split type recited earlier, nevertheless, succeeds in overcoming a major problem in which the split cage is much subject to deformation of bulging radially outwardly at the abutment ends of the cage halves owing to large centrifugal force taking place when the bearing revolves at high speed. This will cause the bearing to seat improperly in the bore surface in the rod big-end of the connecting rod, thus resulting in bearing failure such as lack of lubricating oil, seizing or binding between the bearing and the connecting rod, and so on.
An example of the prior bearing cages of split type envisaged to resolve the problem stated just above is illustrated in FIG. 11. The prior split-type bearing cage 40 is generally composed of a pair of semicircular cage halves 41, which are chamfered at a corner 39 where the abutment ends of the semicircular cage halves 41 merge with the outside peripheral surface of the cage. Rollers 43 are installed in pockets arranged circumferentially of the cage.
With the prior bearing cages of split type constructed as stated earlier, chamfering work on the corners is done to the semicircular cage halves 41, separately, which have been previously prepared by splitting a cylindrical cage stock. This chamfering procedure is much unfavorable for precision control of the chamfered area 39 in size. Thus, not only the chamfered area 39 get scattered in their sizes, but also an edge where the chamfered area merges with the associated outside periphery 42 of the cage will tend to be made much sharp. The tendency will cause any likelihood of raising the lack of lubricating oil, the seizing of bearing and so on at the abutment ends 38 and any area nearby the ends. With the prior bearing cages of split type, moreover, as the cylindrical cage is usually subject to heat treatment in preparatory to cutting into semicircular cage halves 41, the resulting cage halves can not help spreading somewhat radially outwardly at the time of cutting. This also makes it tough to prepare the chambered area at the corner with high precision.
The present invention has for its primary object to resolve the major problem as stated earlier, and to provide a roller bearing cage of split type, which serves useful functions for bearings in, for example a connecting rod in high-compression, high-speed engine and more particularly to a roller bearing cage that is easy in fabrication thereof and precision control of a chamfered area, and further much favorable for the bearings, which are needed to stand up to the harsh conditions imposed by high-compression, high-speed engines.
The present invention is concerned with a roller bearing cage in which a cylindrical cage is split along any diametral plane thereof into a pair of two semicircular cage halves that are arranged in opposition to each other with their mating ends coming into abutment against each other: comprising that the semicircular cage halves are each composed of semicircular rims arranged in a way spaced axially apart from each other and extended circumferentially in parallel with each other, and cage bars positioned between the semicircular rims at regular intervals around curved surfaces of the rims and made integrally with the rims to form a pocket between any two adjacent cage bars, in which a roller is accommodated for rotation; the semicircular cage halves are chamfered off at any outer peripheral areas nearby the mating ends thereby to form chamfered even areas; and the chamfering operation is done preparatory to cutting off the cylindrical cage into two semicircular cage halves.
In one aspect of the present invention there is disclosed a roller bearing cage in which the chamfered even areas on the outer peripheral areas are roughly normal to the mating ends of the semicircular cage halves and also lying on planes that extend in parallel with each other in diametral opposition.
In another aspect of the present invention, there is disclosed a roller bearing cage in which the cage bar having the mating end thereon is roughly equal in circumferential width with other cage bar. Moreover, the cage bars are arranged with their outside surfaces being in flush relation with the outside peripheries of the rims.
In another aspect of the present invention there is disclosed a roller bearing cage in which the cage bar has an inside surface that is sunk at an axial middle area thereof to form a recess extending in depth radially outwardly beyond a diameter across pitch circle on the rollers and in axial length shorter than the pocket, so that the cage bar is made slender at the middle area thereof on account of the recess, with leaving axially opposing ends thereof thick, and circumferentially opposing cheeks of the thick ends provide guide surfaces on which the roller rolls.
In another aspect of the present invention there is disclosed a roller bearing cage in which on the thick ends of the cage bar there are provided outside retainer lugs that jut into the pocket to keep the roller against outward escape out of the associated pocket and inside retainer lugs that also jut into the pocket to keep the roller against inward escape out of the associated pocket.
In another aspect of the present invention there is disclosed a roller bearing cage in which an annular corner where the inside peripheral surface and any one end of the axially opposing end surfaces of the semicircular rims merge with each other is chamfered off into a depth reaching one-third an axial thickness of the associated rim to form a slant annular surface, which slopes to a plane normal to an axial direction of the rim, with an angle less than 45 deg.
In another aspect of the present invention there is disclosed a roller bearing cage in which the edge where the outer periphery of the semicircular rim and the cage bar merges with the associated mating end is chamfered off. The chamfering operation on the areas nearby the mating ends, since done prior to cutting off the cylindrical cage into two halves, allows preparing the chamfered even areas that extend equally over both the semicircular cage halves. Chamfering the edges nearby the mating ends, thus, is beneficial in preventing the bore inside surface in the rod end of the connecting rod against the interference with such edges during rotation of the roller bearing cage, thereby making sure of smooth revolution of the roller bearing cage.
In another aspect of the present invention there is disclosed a roller bearing cage in which a corner where the axial end surface of the semicircular rim merges with the outside periphery of the semicircular rim is slightly rounded.
In a further another aspect of the present invention there is disclosed a roller bearing cage wherein a cylindrical cage is composed of a pair of annular rims arranged in a way spaced axially apart from each other and extended circumferentially in parallel with each other, and cage bars positioned between the annular rims at regular intervals around curved surfaces of the rims and made integrally with the rims to form a pocket between any two adjacent cage bars, in which a roller is accommodated for rotation; the cage bars are arranged with their outside surfaces being in flush relation with the outside peripheries of the rims; the cage bar has an inside surface that is sunk at an axial middle area thereof to form a recess extending in depth radially outwardly beyond a diameter across pitch circle on the rollers and in axial length shorter than the pocket, so that the cage bar is made slender at the middle area thereof on account of the recess, with leaving axially opposing ends thereof thick, and circumferentially opposing cheeks of the thick ends provide guide surfaces on which the roller rolls, and further wherein on the thick ends of the cage bar there are provided outside retainer lugs that jut into the pocket to keep the roller against outward escape out of the associated pocket and inside retainer lugs that also jut into the pocket to keep the roller against inward escape out of the associated pocket.
In another aspect of the present invention there is disclosed a roller bearing cage in which an annular corner where the inside peripheral surface and any one end of the axially opposing end surfaces of the annular rims merge with each other is chamfered off into a depth reaching one-third an axial thickness of the associated rim to form a slant annular surface, which slopes to a plane normal to an axial direction of the rim, with an angle less than 45 deg. Moreover, a corner where the axial end surface of the annular rim merges with the outside periphery of the annular rim is slightly rounded.
In another aspect of the present invention there is disclosed a roller bearing cage in which the slender area of the cage bar is defined in a manner having an inside surface of an axial length extending over a range of from 50% to 80% of an axial length of the pocket.
In another aspect of the present invention there is disclosed a roller bearing cage in which a slant surface connecting the slender area and any one of the thick ends is set to slope to a plane normal to the slender area, with an angle less than 45 deg.
In another aspect of the present invention there is disclosed a roller bearing cage in which the outside retainer lugs formed on the thick ends of the cage bar are designed in such a manner that their radially outside tops are held in flush relation with the outer periphery of the cage bar.
In another aspect of the present invention there is disclosed a roller bearing cage in which an axially middle area of the cage bar is reduced sidewise on circumferentially opposing cheeks thereof to enlarge widthwise the pocket.
In a further another aspect of the present invention there is disclosed a roller bearing cage in which the cage is made in an outside guide construction in which the outside periphery thereof is guided along a bore surface in a rod end of a connecting rod.
With the roller bearing cage of split type constructed according to the present invention, the chamfering operation on the areas nearby the mating ends of the two cage halves is done preparatory to cutting off the cylindrical cage stock into two cage halves. The machining process stated earlier is beneficial in keeping the resulting chamfered areas against getting scattered in their sizes. Thus, this renders the high-precision measurement of the chamfered areas easier, and making sure of process management of material-removal work to make the chamfered areas into a preselected shape. The chamfering operation done on the cage stock prior to the cutoff process, moreover, makes it possible to finish the chamfered areas on the outside periphery with high accuracy. Besides, the chamfered areas are made substantially even and therefore it will be easy to machine any bound between the chamfered even area and the curved surfaces around the roller bearing cage into a smoothly round area. Machining the bound where the chamfered even area merges with the curved surface of the outer periphery into any smooth and round surface serves well to bypass any issue that the outer periphery of the cage might otherwise come into unevenly forced seat at the bounds thereof against the bore surface in the rod big-end of the connecting rod, along which the rollers roll. Thus, the split cage of the present invention is constructed to carry effectively the loads imposed by modern high-speed engines, with no bearing failure.
Cutting off the cylindrical cage stock into two cage halves is done using a wire-electric discharge machining in which the kerf or width of cut is small with a consequently less removal in material than other traditional cutoff machining operations. Thus, the wire-electric discharge machining is in favor of splitting accurately the cage stock into two semicircular cage halves. Chamfering operation using the wire-electrode is preferable for simplifying the machining operations, with even making high-accuracy machining possible.
The roller bearing cage constructed as stated earlier weighs less, making the outer periphery of the cage larger in size, and also is made small in surface-to-surface contact stress that might take place between the bore surface in the rod big-end of the connecting rod and the outer periphery of the roller bearing cage, thus, favorable for carrying the loads imposed by the high-speed revolution, with no occurrence of bearing failure such as the lack of lubricating oil, the seizing of bearing and so on.
Other objects and features of the present invention will be more apparent to those skilled in the art on consideration of the accompanying drawings and following specification wherein are disclosed preferred embodiments of the invention with the understanding that such variations, modifications and elimination of parts may be made therein as fall within the scope of the appended claims without departing from the spirit of the invention.